The invention relates in general to data input mechanism related to an electrical device. In particular the invention relates to an input mechanism especially suitable for small portable communication devices.
A push button or a press key consists of a certain mechanical structure and of an accompanying electrical circuitry. When a user presses a push button or a key of an electrical device, the pressing of a button is converted to an electrical input signal for the device. Typically the mechanical part of a push button requires more space than the accompanying electrical circuitry.
A typical user interface of a portable electrical device comprises at least few push buttons or keys. In a mobile phone, for example, there typically is a display, push buttons for the digits and some push buttons for choosing proper action. As portable electrical devices become smaller and smaller, there is less space for the push buttons. Consider, for example, a communication device that has the shape of a watch, a pen or a pendant.
One solution is to reduce the size of push buttons, but this may result in devices that are difficult to use. Calculator watch having very small push buttons is one example of a device, whose usability is not very good. Another straightforward solution is to reduce the number of the push buttons. The problem here is that although the size of portable communication devices becomes smaller, the functionality such devices is usually similar as that of devices having larger size. Therefore it usually is not feasible to reduce the number of push buttons. Further reasons for reducing the number of push buttons are, for example, the aim to design classy devices and the aim to obtain a simple and robust structure.
A prior art push button or keyboard, where the pressing of a button is converted into an electrical signal, works usually in the following way. When a button is pressed down, an electrical contact is formed between two conductor strips, and when a button is in the rest position, there is no electrical contact between the conductor strips. Typically the mechanical structure of a push button is such that it automatically returns to the rest position (up position), when a user stops pressing the button.
FIG. 1 shows a cross section of a typical push button structure according to prior art. A button 104 typically has an upper part having a smaller diameter and a base, which has a larger diameter and is hollow. The button refers here to the plain button 104, and term push button refers to the whole mechanical construction including the button 104. The surface of a button 104, which faces the circuit board 101, is typically a circular rim. In the bottom of a button 104 there is a hole, which allows the housing of a dome 102. When the button is in the up position, there is room for the dome 102 to be in its normal position. The button 104 has an actuator 105, which presses the dome 102 down when the button 104 is pressed down. The dome 102 acts as a spring, and as a user stops pressing the button 104 down, the dome returns to its normal position and simultaneously pushes the button back to the up position. The actuator 105 is necessary, because if the whole surface of the button 104 would be pressed against the dome 102, the spring effect of the dome 102 might be lost and the force needed to press the lower surface of the dome in contact with the circuit board 101 would be larger than when an actuator 105 is used. Typically the upper part of the button 104 is rigid, and the movement of the button 104 in the vertical direction is due to the thin rim connecting the upper part and the base of the button 104. The material of the button 104 has to be elastic enough for allowing the rim to flex. A button 104 can be made, for example, of rubber.
The circuit board 101 comprises the necessary circuitry for detecting the pressing of a button 104. A conductive area in the lower surface of the dome 102 is pressed against, for example, two conductor strips 107, and an electrical contact between the conductor strips indicates the pressing of a button. If the whole dome is made of conductive material, there may be a separate isolating layer 103 to isolate the rim of the dome from the conductive strips. Another way to isolate the rim of the dome from the circuitry is to use multilayer circuit board. A further option is to make the dome of an isolating material and to deposit a conducting layer in a suitable area of the concave surface of the dome 102.
FIG. 1 shows also a cover 106, which has holes for the buttons. Typically the profile of a cover is not uniform to minimize the material needed for the cover and the mass of the cover. The height of a button 104 is usually few millimeters. The buttons of a keyboard are typically connected to each other at their base parts and they form a key mat. Typically it is quite difficult to obtain a waterproof push key mechanism, because it is difficult to fix a cover, which may have a non-uniform profile, and a key or a key mat to each other tightly.
In a mobile communication device there is typically a keyboard for inputting digits, some separate push buttons and a display in the front surface of the device. The smaller the device, the smaller usually the front surface and the less space for the display and the various push buttons. It typically is necessary to reserve enough room, for example, for the display. If the push buttons are made too small, it is difficult to press a correct button. Therefore reducing the size of the buttons is not a good solution. Furthermore, having many small buttons in a small device usually does not give the impression of a classy, well-designed device. The mechanical structure of small push buttons may also cause some problems. These problems arise also if small push buttons are placed in the side surface of a device. Another solution is to reduce the number of the push buttons, but unfortunately the functionality of communication devices is typically so versatile that to use conveniently a communication device, the device typically has to have at least few push buttons.
For design purposes and for achieving waterproof device, it may be advisable to eliminate the need for push buttons. One way to do this is to use a touch sensitive display. The advantages of a touch sensitive screen include at least the freedom to design a device without push buttons and to use the same area both as a display and as an input means. The disadvantages of such a display are that it is relatively expensive and that is lacks the tactile feel of a push button. The user cannot feel when he is pressing a key, or actually pointing a certain position on the display. The sense of pressing a button typically makes the use of a device more comfortable.
Patent application WO 98/29886 presents a way to integrate push button functionality and a display. A first plate of the display structure is arranged, using hinges, to tilt when the display is pressed. The first plate has conductive actuators extending from one surface and there are corresponding conductive coupling areas on the surface of a second plate. The display can be mounted so that the first plate can be tilted around an axis. This way it is possible to place two conductive actuators to the first plate. If the first plate is supported in one point in the middle of the plate, more conductive actuators, for example four, can be placed to the first plate. A contact between a conductive actuator and a conductive coupling area is made by tilting the first plate. The construction of the virtual touch screen presented in WO 98/29886 is complex and requires many separate parts. It is therefore most probably quite a difficult and expensive solution. Furthermore, it is not easy to make a waterproof device using this virtual touch screen.
An object of the invention is to present a data input mechanism, which acts as a set of push buttons or as a keyboard and also as another part of an electrical device. A further object of the invention is a data input mechanism, which preserves the tactile feel related to push buttons. A further object of the invention is a data input mechanism, which acts as a display and a set of push buttons. Preferably the data input mechanism is waterproof and simple to construct.
Objects of the invention are achieved by covering the domes relating to an electromechanical data input mechanism with a single movable part, which comprises actuators and is kept apart from a second part, which comprises conductive coupling areas related to domes, through the domes.
An electromechanical data input mechanism according to the invention comprises
a first structural entity,
a second structural entity arranged to move with respect to said first structural entity,
as a part of said first structural entity, a first surface,
as a part of said second structural entity, a second surface located adjacent to said first surface and separated therefrom by a gap,
a conductive coupling area on said first surface,
between said first and second surfaces and adjacent to said conductive coupling area a dome-like member having a conductive surface adjacent to the conductive coupling area, and
extending from the second surface, an actuator located adjacent to each dome-like member, and provides a pressing area, for exerting a force pressing the first and second structural entities towards each other, substantially within which pressing area the dome-like member is located, and the mechanism is characterized in that
within the pressing area, elastic properties of the second structural entity are substantially uniform,
said first and second structural entities are within the pressing area kept apart from each other solely through the dome-like members, and
under the influence of a pressing force exerted on an area within the pressing area and pressing the first and second structural entities towards each other, said first and second structural entities are arranged to move, with respect to each other, so that the actuator moves towards the dome-like member.
The invention relates also to an electronic device comprising an electromechanical data input mechanism, which electromechanical data input mechanism comprises
a first structural entity,
a second structural entity arranged to move with respect to said first structural entity,
as a part of said first structural entity, a first surface,
as a part of said second structural entity, a second surface located adjacent to said first surface and separated therefrom by a gap,
a conductive coupling area on said first surface,
between said first and second surfaces and adjacent to said conductive coupling area a dome-like member having a conductive surface adjacent to the conductive coupling area, and
extending from the second surface, an actuator located adjacent to the dome-like member, and which mechanism provides a pressing area for exerting a force pressing the first and second structural entities towards each other, substantially within which pressing area the dome-like member is located, and the electronic device being characterized in that
within the pressing area, elastic properties of the second structural entity are substantially uniform,
said first and second structural entities are within the pressing area kept apart from each other solely through the dome-like members, and
under the influence of a pressing force exerted on an area within the pressing area and pressing the first and second structural entities towards each other, said first and second structural entities are arranged to move, with respect to each other, so that the actuator moves towards the dome-like member.
An electromechanical data input mechanism according to the invention comprises two structural entities, which are typically substantially plate-like at least at the pressing area, and the actuators relating to the input mechanism are part of the second structural entity. It further comprises at least one dome-like member between a first surface, which is a part of the first structural entity, and a second surface, which is a part of the second structural entity. At least one actuator extends from the second surface, and there is at least one connective coupling area on the first surface. There is a gap between the first and second surfaces and the dome-like member is adjacent both to a respective actuator and to a respective conductive coupling area. Each dome-like member has a conductive are facing the respective conductive coupling area.
When a force, which presses the first and second structural entities towards each other is exerted, the first and second structural entities are arranged to move with respect to each other. The first and second structural entities are kept apart from each other by the dome-like members within the pressing area. Outside the pressing area it is possible that the first and second structural entities are mechanically coupled to each other. Despite a possible mechanical coupling outside the pressing area, the dome-like members dictate at lower limit for the distance between the first and the second structural entities at the location of the domes, and as the dome-like members change their shape, the distance between the first and second structural entity changes. At the location, where a dome is, the distance between the first and second structural entity can be larger than the height of a dome, but it cannot be smaller. With respect to an inertial coordinate system, either the first structural entity, the second structural entity or both the entities can move. In a electromechanical data input mechanism according to the invention, the first and second structural entities are arranged to move with respect to each other, under the influence of a pressing force exerted on a certain area within the pressing area, typically near an actuator, so that the actuator moves towards a respective dome-like member. The elastic properties of the second structural entity are substantially uniform within the pressing area. The elastic properties of the second structural entity are different at the locations of the actuators than in the area surrounding the actuators, but as the area of an actuator, which is typically only about a square millimeter, is very small compared to a typical pressing area of several square centimeters, the elastic properties in these point-like areas are insignificant when the whole second structural entity is considered. For example, if the second structural entity is a plate having a uniform thickness and having the actuators as extension on one of its surfaces, the elastic properties of the second structural entity are in this case dominated by the elastic properties of the plate and they are, consequently, substantially uniform. Especially, each actuator is not surrounded by a zone, which allows the actuator to move independently of the rest of the second structural entity. In an electromechanical data input mechanism according to the invention, a quite large portion of the second structural entity moves similarly as the actuator, and typically the movement of an actuator may cause also neighboring actuators to move slightly.
The first structural entity and the second structural entity can be substantially rigid entities, in which case the structural entities, under the influence of a force pressing them towards each other, typically tilt with respect to each other. It is also possible that the elastic properties of at least one of the first and second structural entities are arranged to be such, that an actuator together with a larger portion of the second structural entity moves towards the dome-like member because the first structural entity and/or the second structural entity bends.
Typically when the conductive area of a dome-like member touches the conductive coupling area, an electrical signal is generated, and this electrical signal is treated as an input signal. Typically there is a related electrical circuitry, which generates the electrical signals. In an electromechanical data input mechanism according to the invention, the first and second structural entities are typically arranged to move so much that the actuator presses the conductive area of the dome-like member against the conductive coupling area, which is on the surface of the first structural entity.
The number of dome-like members in an electromechanical data input mechanism according to the invention is at least one. Typically a few, for example four, dome-like members can be used, but it is also possible to have several dome-like members between the first and the second structural entities. Especially if the pressing area, within which the dome-like members typically are, is large and the functionality of an electromechanical data input mechanism according to the invention is based on one of the first and second structural entities to bend locally, the data input mechanism can comprise a large number of dome-like members.
The structure of an electromechanical data input mechanism according to the invention is simple and robust. The actuators are part of the second structural entity. They can be either made of the same material, for example during casting (e.g. injection molding or sheet metal forming) or they can be made of different material and be fixed to the second member, for example, using suitable adhesives. The assembly of a data input mechanism according to the invention is simple, because the number of parts is quite small. Separate buttons or key maps are not needed, and as a key mat, for example, is quite heavy compared to other parts of a small portable device, the weight of a portable device can also be reduced. The reduced amount of required material and the easy assembly also reduce costs. It is possible to make an electromechanical data input mechanism according to the invention waterproof quite easily, for example, by filling the gap between the first and second structural entities with suitable elastic material, which allows the first and second structural entities to move with respect to each other so that a conductive area of a dome-like member can be pressed against a conductive coupling area.
As a user presses the first and second structural entities towards each other, he can feel how the spring-like effect related to the dome-like member. The dome-like member resists slightly the pressing and, after its conductive area has been in contact with the conductive coupling area, it tries to retain its original shape, similarly as in conventional push button structures. Consequently, the user has a good tactile feel. This is one of the advantages of the invention.
A further advantage of the invention is that a certain area of the surface of an electronic device can be employed as an electromechanical data input mechanism in addition to another function. For example, in an area, where there is a display, an electromechanical data input mechanism according to the invention can be placed. It is also possible that a substantially thin cover of a device or a window of a device acts as the first or second structural entity of an electromechanical data input mechanism according to the invention. This way also the weight and size of a device can be reduced without cutting functionality of the device or reducing the usability of the device. Furthermore, an industrial designer has a more freedom to design a device, when an electromechanical data input mechanism according to the invention is used, because a need for separate push buttons can be eliminated using the invention.